1. Field of the Invention
This invention relates to a process for preparing shaped articles of rigid rod heterocyclic liquid crystalline polymers.
2. Description of the Prior Art
The preparation of shaped articles, such as fibers, filaments, yarns, and films composed of polybenzothiazoles is known in the art. In U.S. Pat. No. 3,681,297, a selected dialdehyde is reacted with a defined aromatic bismercaptoamine to obtain a polybenzothiazoline. This material is then subjected to oxidation to obtain the related polybenzothiazole. In the event that unconverted reactants remain, the patent discloses that the polymer may be heated in excess of 175.degree. C., preferably in the range of 250.degree.-400.degree. C. in nitrogen or 250.degree.-350.degree. C. in air to cause chain extending polymerization.
In U.S. Pat. No. 4,051,108, two-dimensional microscopic sheets or coatings are formed by initially dissolving a formed para ordered aromatic heterocyclic polymer in a polymer solution such as methanesulfonic acid. The polymer solution is added to a non-solvent for the polymer thereby causing the polymer to precipitate. The polymer particles are collected by filtration, such as by using a fritted glass filter, or by dipping an object in the dispersion. Evaporation of the solvent can be accelerated by employing a forced air oven. A similar technique is described in U.S. Pat. No. 3,987,015.
In U.S. Pat. No. 3,313,783, high molecular weight polybenzimidazoles are prepared by reacting at least one inorganic acid salt of an aromatic tetra-primary amine and at least one dicarboxylic acid or derivative thereof in a polyphosphoric acid medium at an elevated temperature in the range of from 100.degree. to 250.degree. C.
In U.S. Pat. No. 4,225,700, poly [benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene is prepared by reacting 2,5-diamino-1,4-benzenedithiol dihydrochloride with terephthalic acid in polyphosphoric acid. The polymerization mixture is precipitated into water and successively washed with water, dilute ammonium hydroxide and then water. Alternatively, the mixture is combined with methanesulfonic acid, precipitated into methanol and successively washed with water, aqueous ammonium hydroxide and methanol and then freeze dried from benzene.
In U.S. Pat. No. 3,574,170, poly(bisbenzimidazobenzophenanthroline) is prepared by reacting at least one organic tetra-amine with at least one tetracarboxylic acid or its corresponding dianhydride. The patent refers to a concurrently filed U.S. application Ser. No. 867,880 (now abandoned), which application describes a process for preparing shaped articles of the specified polymer by direct extrusion of the polymerization medium into a coagulation bath. Similarly, wholly aromatic carbocyclic polycarbonamide shaped articles may be prepared from the polymerization medium as disclosed, for example, in U.S. Pat. No. 3,819,587.
No prior art of which applicants are aware discloses or suggests that shaped articles of rigid rod heterocyclic liquid crystalline polymers, particularly poly [benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene may be prepared directly from the reaction mixture.
In application Ser. No. 483,799 now U.S. Pat. No. 4,554,119 issued Nov. 19, 1985 filed concurrently herewith by Edward C. Chenevey, entitled "Process for Heat Treating Shaped Articles of Poly [benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene, Its Cis Isomer or Mixtures Thereof and the Articles Formed Thereby" and assigned to an assignee of the present application, there is described a process for simultaneously heating and stretching shaped articles of the defined polymer.
In application Ser. No. 483,797 now U.S. Pat. No. 4,487,735, issued Dec. 11, 1984 filed concurrently herewith by Edward C. Chenevey and Ronald Kafchinski, entitled "Process for Preparing Film of Poly [benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene, Its Cis Isomer or Mixtures Thereof" and assigned to an assignee of the present application, there is described a process for preparing film of the polymer by extruding it on a casting roll, subjecting it to elevated temperatures and, preferably, heat treating it.